1. Field of the invention
This invention relates to a cleaning member for removing condensation and ink wetness created on the ink discharge port surface of a recording head carried on an ink jet recording apparatus applicable to an apparatus using an ink jet recording apparatus as the output unit of an image display apparatus or an image forming apparatus, such as a coyping apparatus, a facsimile apparatus, an electronic desk top calculator, a typewriter, a printer as the output unit of a computer or the like, or a composite apparatus, and an ink jet recording apparatus provided with the cleaning member.
2. Related Background Art
As the main current of the ink jet recording system, mentioned may be made of the system using a piezo-electric element and the bubble jet system which is compact and can accomplish formation of liquid droplets well represented by Japanese Patent Publication No. 61-61985. These systems form a liquid droplet in comformity with a desired electrical signal, and causes the discharged liquid droplet to adhere to a recording medium spaced apart from the discharge port of an ink jet head to thereby accomplish printing or image formation.
In a recording apparatus to which this ink jet recording system is applied, it has sometimes happened that water content contained in ink and a recording medium is evaporated to make the atmosphere of the recording head highly humid and cause condensation to occur on a surface in which the ink discharge port of the recording head is formed, depending on conditions such as the temperature of the recording head and of its atmosphere.
It has also sometimes happened that droplets resulting from the rebound occurring when the discharged ink impacts a recording medium, or minute ink droplets other than the liquid droplets discharged from the discharge ports and the satellites thereof adhere to the discharge port surface (i.e., the surface of the head). When condensation thus occurs on the discharge port surface or minute ink, droplets adhere to the discharge port surface, it has sometimes happened that the original function of the apparatus is degraded and discharge from some discharge ports becomes difficult or the direction of discharge is changed. That is, when condensation or wetness occurs on the discharge port surface, waterdrops or the like adhere to the discharge port surface, and these adhering waterdrops or the like pull discharged ink non-uniformly when ink is discharged from the discharge ports. Thereby, irregularity of the direction of discharge and the speed of discharge of the ink and the diameter of ink droplets results, thus deteriorating the quality of recording. Also, the wetness of the discharge port surface makes paper powder, dust and the like likely to adhere to the discharge port surface. Therefore, these conditions adversely affect the direction of discharge of the ink or cause the discharge ports to be clogged, and this has sometimes become a cause of the deteriorated quality of recording. The phenomenon such as the above-described condensation or wetness has become more remarkable where a fixation heater is used to expedite the fixation of recorded images on a recording medium or where the dot duty of recorded images is high.
In order to solve this phenomenon, it has been conceived and proposed to clean the discharge port surface and remove condensation, wetness and the like.
Firstly, wiping the discharge port surface by the use of a solid rubber blade or a metallic blade is mentioned, and secondly, wiping the discharge port surface by an absorbing member is mentioned.
The wiping by an absorbing member is not known in detail as in Japanese Laid-Open Patent Application No. 57-61574 (detailed description thereof is not made therein), and the use of a porous substance and the use of Japanese paper or cloth as in Japanese Laid-Open Patent Application No. 57-80064 and Japanese Laid-Open Patent Application No. 57-116655 have been proposed, but have not yet be put into practice.
On the other hand, a construction in which, unlike the usual cleaning for the purpose of washing the discharge port surface, a sponge impregnated with ink-soluble liquid is caused to bear against the discharge port surface and apply the liquid to the discharge port surface is disclosed in Japanese Laid-Open Patent Application No. 59-164149.
On the other hand, as a method of wiping the discharge port surface by a rubber blade, mention may be made of Japanese Laid-Open Patent Application No. 52-102728 (German Patent Publication DE-OS-2607313.2) and Japanese Laid-Open Patent Application No. 61-230949.
In numerous patent citations showing rubber solid blades, including these, only the construction thereof is shown. Of course, the effect of cleaning the discharge port surface by the use of these blades is recognized.
For example, if cleaning is not performed, as shown in FIG. 1 of the accompanying drawings, a so-called "leak condition" 3 of ink such as minute ink droplets and ink droplets made gigantic by the aggregation thereof is created on a head surface (discharge port surface) 2 which is a surface in which discharge ports are formed. In the on-demand type ink jet system particularly like the BJ (bubble jet) system, this occurs when the duty or rate of discharge becomes high. Also, in the continuous injection type ink jet system described in U.S. Pat. Nos. 3,373,437, 3,298,038 and 3,416,153, recording liquid is continuously discharged from discharge ports and therefore, "leak" occurs more readily.
FIG. 2 of the accompanying drawings shows the result of wiping the condition of "leak" indicated by 3 in FIG. 1 substantially perpendicularly to the direction of arrangement of discharge ports 8 by the use, for example, of an elastic blade chiefly of silicone rubber or urethane rubber having a conventional construction (this is a conventional cleaning method).
For example, where use is made of a blade of silicone rubber having a hardness of the order of 40.degree. and a thickness of the order of 0.2-0.6 mm to a relatively small thickness of 0.2-0.4 mm determined so as not to damage, for example, the coating or the like of the discharge port surface by the elastic force of the blade, it has sometimes been the case that the pressure contact force of the blade to the discharge port surface is not sufficient and therefore water content, dust, etc. adhering to the discharge port surface of the recording head cannot be completely removed.
In contrast, if the thickness of the silicone rubber is made relatively great, e.g. 0.4-0.6 mm, the pressure contact force becomes sufficient and water content dust, etc. adhering to the discharge port surface of the recording head can be removed well, but if the wiping operation is performed 300,000 times or so, it has sometimes been the case that the silicone material abraded thereby adheres to the discharge port surface and discharge ports of the recording head and the unsatisfactory discharge as described above occurs.
In addition, with regard particularly to the state of pressure contact between the blade and the discharged port surface, in order to forcibly clean the discharge port surface, it has been proposed to use a relatively high pressure of line pressure 25 g/cm or more as the pressure of contact between the discharge port surface and the blade to thereby enhance the cleaning effect. The line pressure herein referred to is the load divided by the length of contact.
As a problem resulting from the high pressure of contact, it has happened that the friction of the blade itself occurs to deteriorate the durability of the blade. Particularly, where the discharge port surface is treated with a water-repelling agent to form a condition in which it is difficult for ink to adhere to the discharge port surface, i.e., a condition in which the discharged port surface can be readily cleaned, it has been found that the water-repelling agent is removed by this high pressure and all the more, unsatisfactory cleaning occurs.